1. Field of the Invention
This invention relates to a free-wheel hub with a coaster brake for use in a bicycle.
2. Description of the Prior Art
One type of the free-wheel hub with a coaster brake to which the present invention pertains is disclosed in Japanese Utility Model Publication No. 44-5464 published on Feb. 27, 1969 with the same assignee as the present invention. The free-wheel hub disclosed therein is illustrated in FIGS. 1 and 2, from which it is seen that the free-wheel hub 10 with a coaster brake is employed in the rear wheel D of the bicycle in FIG. 1, in which a selected one stand of a multistand driving change gear 12 is driven by pedalling a pedal A clockwise through an endless driving chain B spanned across a front driving gear C and the driving change gear 12 while a braking gear 14 is rotated by pedalling the pedal A counterclockwise through an endless braking chain B1 spanned across a front braking gear C1 and the braking gear 14. The driving force from the driving change gear 12 is transmitted to a hub cylinder 16 through a ratchet 18 and bearings 20 to drive the rear wheel D incorporating the hub cylinder 16, which results in running the bicycle forward. On the other hand, during the braking mode operation, the braking gear 14 mounted on a braking male screw cylinder 22 permits a braking female screw cylinder 24 thread engaged to the braking male screw cylinder 22 to shift axially leftward as viewed in FIG. 2. The braking female screw cylinder 24 pushes a clutch 26 through a clutch spring 28 toward brake discs 29 sandwiching rotary discs 30 rotatably free from a brake holder 32 fixed to a shaft 34. The rotary discs 30 are accordingly pressed by the clutch 26 while the rotary discs 30 are being rotated with the hub cylinder 16 through the grooves provided on the inside wall of the hub cylinder 16, so that the brake discs 29 are subjected to the braking force from the clutch 26, resulting in braking the rear wheel D of the bicycle.
The conventional coaster brake is constructed such that the following disadvantage is inevitable. Namely, when one pushes the bicycle backward without riding thereon, the rear wheel D of the bicycle is rotated counterclockwise in FIG. 1 thereby naturally rotating the hub cylinder 16 in the same rotating direction. At this time the adaption of the ratchet 18 to the engagement between the driving change gear 12 and the hub cylinder 16 causes the driving change gear 12 to rotate in the same rotating direction as the hub cylinder 16. Then the driving change gear 12 rotates the front gear C together with the front gear C1 through the driving chain B and therefore the braking chain B1 due to the front gear C1 rotating the braking gear 14, whereby the braking mode operation is carried out in the same way as above described, resulting in braking the bicycle. Thus the conventional bicycle employing such a coaster brake experiences this difficulty in pushing it backward.